I am not a judge but knowing several I know that it is a tough job tasting beer all day, or in some cases over several days. Some samples tremendous and some are down right nasty.
I think the judges, whether they are nationally ranked or just getting started, do their very best to fairly evaluate each and every beer, but yes, regardless of what score you get or comments you receive, take it for what it's worth-an opinion.
In the end, if you like your beer and are proud of it then enjoy it! Take the feedback you receive and apply the parts that you think could improve the beer and forget about the comments you might not agree with. I also find that when possible, enter the same beer in several comps to get a better overall feel of the beer.
It is also important to provide feedback to the judges on their evaluations. I have emailed several judges from various comps to get a better understanding of their comments and attach their score sheets so they can remember what they wrote as well, even if they don't recall the specific beer. For example: In my most recent comp my ESB received a 35 which I was happy with. The problem though was after reading one judges comments I found that his understanding of the style was lacking. Each thing I got dinged for is clearly stated in the guidelines as being true to style and more than acceptable. In a polite manner I emailed him a copy of the sheet and a suggestion that he re-read the style guideline so that he can improve his understanding and improve his judging knowledge. This was a "recognized" judge and his score brought my average down.
Judges are constantly learning their trade just like brewers. They take the time to volunteer but I also believe that as a brewer it is my right to provide them feedback as well, both positive and negative so they too can improve their trade.
As previously mentioned, you are dealing with the personal abilities of each judge to properly sample your beer and each person's ability to note certain characteristics will be different. Each person's threshold of taste will be different. I can easily detect most general flaws in a beer but when it comes to discerning the nuances of certain hops or malt profiles I fall short. In many cases I can even tell you what yeast was used in a beer while others can't, every one has strengths and weaknesses. It is unfair to lump all judges together and call them biased.